Osteoradionecrosis of the Mandible

Robert Marx, D.D.S. has provided several key principles in the understanding of the pathophysiology of mandibular necrosis and its management. He has demonstrated that infection is not the primary etiology of mandibular necrosis by obtaining deep cultures of affected bone and showing the absence of bacteria.

We now understand that Osteoradionecrosis is the result of avascular aseptic necrosis. Marx has also shown that for hyperbaric oxygen to be consistently successful, it must be combined with surgery in the optimal fashion. Marx has developed a staging system for classifying mandibular necrosis. This staging system is applied to determine the severity of mandibular necrosis. In addition it permits a plan of therapeutic intervention, which is a logical outgrowth of the stage of necrosis.﻿

Stage I ORN (Osteoradionecrosis) includes those patients with exposed bone who have none of the serious manifestations of those in Stage III. Generally these patients have had chronically exposed bone or they have rapidly progressive ORN. These patients begin treatment with 30 HBO 2 sessions with either no debridement or only minor bony debridement planned. If these patients progress satisfactorily an additional 10 treatments are given. If patients are not progressing appropriately or if a more major debridement is needed, they are advanced to Stage II and they receive the necessary surgical debridement at 30 treatments followed by 10 post-operative treatments.

Surgery for Stage II patients must maintain mandibular continuity. If mandibular resection is required, patients are advance to Stage III. Patients who present with grave prognostic signs such as pathologic fracture, orocutaneous fistulae or evidence of lytic involvement extending to the inferior mandibular border are treated as in Stage III from the outset. Patients from Stage I or II can also be advanced to this stage if they do not make appropriate progress. In Stage III patients are entered into a reconstructive protocol where a mandibular resection is followed by a planned reconstruction.

Marx has established the principle that all necrotic bone must be surgically eradicated. Stage III patients receive 30 hyperbaric treatments prior to their resection followed by 10 post-resection treatments. Typically after a period of several weeks, the patients complete a reconstruction which may involve various surgical techniques including free flaps or myocutaneous flaps. In its original design, the reconstruction made use of freeze-dried cadaveric bone trays from a split rib or iliac crest combined with autologous corticocancellous bone grafting. In his original work at Wilford Hall USAF Medical Center, Marx had reconstruction patients complete a full additional course of hyperbaric treatments in support of the reconstruction. He has now shown that the vascular improvements accomplished during the initial 40 hyperbaric exposures are maintained over time and patients can undergo reconstruction without the second full course of HBO2. Patients do receive 10 hyperbaric treatments after the reconstructive surgery to support tissue metabolic demands.

Marx has reported his results in 268 patients treated according to the above protocol. In his hands with this technique, successful resolution has been achieved in 100% of patients.

Extraction of teeth from heavily irradiated jaws is a common precipitating factor for mandibular necrosis. Marx has published the results of a randomized prospective trial wherein patients who had received a radiation dose of at least 6,800 cGy were randomly assigned to pre-extraction HBO2 versus penicillin prophylaxis. Those patients assigned to the hyperbaric group completed 20 pre-extraction HBO2 treatments with 10 additional post-extraction hyperbaric treatments.

Thirty-seven patients were treated in each group. In the penicillin group, some 29.9% of patients developed ORN while only 5.4% of patients in the hyperbaric group developed necrosis. Also the severity of ORN was more pronounced in the penicillin group with nearly three-quarters requiring treatment as Stage III patients while neither patient with ORN from the hyperbaric group required a discontinuity resection and both resolved as Stage I ORN patients with additional hyperbaric oxygen.

The important principles (advocated by Marx) in the treatment and prevention of ORN include an emphasis on pre-surgical hyperbaric oxygen to allow better tolerance to surgical wounding. The need to eradicate all necrotic bone surgically is also emphasized. In the tissue deficient patient the use of myocutaneous flaps are routinely employed.

* The above information is from the 2003 Hyperbaric Oxygen Therapy Committee Report by John Feldmeier, D.O. et al.